Washing machine appliances generally include a cabinet which receives a tub for containing wash and rinse water. A wash basket is rotatably mounted within the wash tub. A drive assembly is coupled to the wash tub and configured to rotate the wash basket within the wash tub in order to cleanse articles within the wash basket. Upon completion of a wash cycle, a pump assembly can be used to rinse and drain soiled water to a draining system.
Washing machine appliances include vertical axis washing machine appliances and horizontal axis washing machine appliances, where “vertical axis” and “horizontal axis” refer to the axis of rotation of the wash basket within the wash tub. Vertical axis washing machine appliances typically have the wash tub suspended in the cabinet with damping devices. Vertical axis washing machine appliances exhibit vibration harmonics and work in a wide range of rotational speeds.
Many previously known damping devices are fixed friction damping devices which are tuned to one condition that requires the greatest amount of friction. Such fixed friction type damping devices, however, may poorly accommodate the wide range of mass, imbalance, and rotational speed seen in vertical axis washing machine appliances. More recently, various two-stage damping devices have been utilized. These devices provide minimal or no damping under certain conditions and substantial damping under other conditions. Such devices do not adequately address the wide range of mass, imbalance, and rotational speed seen in vertical axis washing machine appliances. Still further, the use of active dampers has been contemplated. However, such dampers are generally considered cost-prohibitive for washing machine appliance applications.
Accordingly, a need exists for improved damping devices for use in washing machine appliances. In particular, damping device which includes variable damping features for varying the damping force generated by the damping device would be advantageous.